Why You Feel the Burning Sensation When Eating Peppers

Capsaicin is the substance in chilies that makes the brain believe that they are hot. Even if you don’t get any burns, and it required very large amounts of chili for it to be dangerous – so the brain can be very convincing…


Scoville Scale

The Scoville scale provides a guide to how strong different chili varieties are. Note, the values are approximate because the amount of capsaicin varies in the different peppers of the same type.

Capsaicin is found in the fruits from the genus Capsicum, but the content varies greatly. From peppers lack capsaicin to the really strong chilies like Habanero, Bhut Jolokia, and the currently strongest – the Carolina Reaper.

A common misconception is that the seeds are the strongest part of a chili.  This is not true! The seeds have a quite low content of capsaicin, but because the largest concentration is found in the placenta (the white mass of which the seeds are attached to) so it is easy to understand the confusion.

Scoville Heat Units

The strength of a pepper is measured in Scoville Heat Units (SHU). Originally, the method was that they measured how many times they could dilute the chili purée and three experts still could notice the strength. A strength of 1,000 SHU meant that it just went to notice burning sensation of capsaicin of a milliliter of the purée in a gallon of water. A strength of 400,000 SHU (e.g., Habanero) means that one milliliter of the paste is possible perceivable in 400 liters of water.

Nowadays the heat is measured laboratories, but it is still no certain measures, because the concentration of capsaicin varies from fruit to fruit depending on growing conditions.


Why Chili Peppers Burn


  • Capsaicin stimulates the same neurons that detect heat. It makes the brain to believe that we are burned.
  • Normal amounts of chili (or mild to medium peppers) in the food makes us experience heat – it tastes strong.
  • If we increase the number of peppers (or use a hotter pod) your mouth will feel numb. This is because the body releases endorphins to deal with the perceived heat.
  • Really high levels of capsaicin can cause contact dermatitis in sensitive people and this can show itself as blisters. This has sometimes been understood as extremely strong chili can cause burns, but it is not true.
  • High doses can irritate the skin, but we will not get scorched


The Hottest Peppers in the World


Bhut Jolokia, also called Ghost pepper, was dubbed world’s strongest chili peppers in 2012.  It is more than 400 times stronger than the tabasco sauce.

One of the hottest peppers in the world is Bhut Jolokia

Bhut Jolokia (Photo: Richard Elsey, Flickr)

In 2013, however, Bhut Jolokia was succeeded in 2013 by the Trinidad moruga scorpion.

Currently, it is the Carolina Reaper that is the hottest pepper in the world (according to the Gunnies World Records).

In 2017 rumors started to appear that a pepper known as the Dragon’s Breath is the hottest pepper in the world. However, this has yet to be confirmed (see here, for instance).


To eat really strong chili is a both painful and unpleasant experience – but hardly fatal. You have to eat over a kilogram of the strongest pepper to ingest a lethal dose of capsaicin.

If you happen to eat too much chili, don’t drink water! Capsaicin is a fat-soluble substance and the water will only spread the pain further. Therefore, a glass of fat milk or cream is the best way to relieve the pain of eating too much chilies.

See our post The 10 Hottest Peppers in the World if you want to know a bit more about this.

The Carolina Reaper

Carolina Reaper (Photo: Richard Elsey, Flickr)

Birds don’t feel the heat

It has been reported that a few people in the world who don’t have nerve receptors that react to capsaicin.  These people can eat large amounts of without the stingy sensation most of us get.

Interestingly, birds don’t have these receptors. This is probably a genius way for the plant to ensure their seeds are spread and more plants will grow. Whereas mammals chew the seeds, birds eat them the whole.

There are many uses for hot peppers, not just cooking. Medically it is used in skin creams to reduce the muscular pain and has also been shown to be effective against psoriasis. Some studies have shown that capsaicin can also be used in the treatment of cancer but there is no definitive research that shows this.

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